The purpose of this application is to investigate and develop laser photoradiation therapy (PRT) of malignant tumors. Studies will be conducted on cells in vitro, animals and humans. The dye hematoporphyrin derivative (HPD) will be used to selectively sensitize malignant cells to red laser light, so that upon exposure to the light a series of photochemical reactions will occur eventually resulting in the release of singlet oxygen, which is cytoxic. This technique has been recently developed by other investigators, and it is one of our major goals to fully evaluate and improve upon the current methodologies. We will investigate the parameters of HPD exposure, laser wave-length, laser dosimetry, time from HPD treatment to laser treatment in order to optimize and better define the delivery modalities. We will also expend considerable effort to elucidate the cellular mechanisms of HPD + light effects. These studies will be conducted in various cellular and animal systems and will employ cytological, ultra structural, and spectrophotometric methods. Effort will also be devoted to determining if tumor fluorescence can be used to calculate dose of laser therapy, since HPD is highly fluorescent. Extensive patient trials will be undertaken to explore the use of PRT as both a palliative and curative mode of management of solid tumors recurrent to the chest wall and tumors of the head and neck.